Varicella zoster infection (chickenpox)

Question 1

What type of virus is varicella zoster?

Answer 1

DNA virus

Question 2

What is varicella zoster responsible for?

Answer 2

Chickenpox - primary infection

Shingles - viral reactivation

Question 3

What percentage of the antenatal population are seropositive for the varicella zoster IgG antibody?

Answer 3

90%

Question 4

What is the incidence of chicken pox in pregnancy

Answer 4

3 in 1000

Question 5

How does primary varicella zoster infection typically present?

Answer 5

Fever
Malaise
Pruritic maculopapular rash - becomes vesicular and crusts before healing

Question 6

What is the incubation periodof varicella zoster?

Answer 6

10-21 days

Question 7

How long is a woman infectious with varicella zoster for?

Answer 7

48hrs prior to the rash until the vesicles have crusted

Question 8

What is varicella zoster infection associated with?

Answer 8

Pneumonia
Hepatitis
Encephalitis

Question 9

What percentage mortality in mothers does varicella zoster pose?

Answer 9

2%

Question 10

What investigations are done in varicella zoster?

Answer 10

Clinical diagnosis - history and examination

Diagnostic doubt - immunofluorescence of basal epithelial cells scrapped from vesicle or PCR for varicella zoster DNA. Immunity status - test for IgM and IgG antibodies to varicella zoster

Question 11

How is varicella zoster in pregnancy managed?

Answer 11

Suspected varicella contact - if mother describes previous primary varicella zoster infection assume immunity, if no previous infection varicella zoster IgG testing is required to confirm immunity status. If not immune, give varicella zoster immunoglobulin (VZIG) within 10 days of contact and before any rash appears

Maternal chickenpox - aciclovir (800mg PO 5times a day) within 24 hrs of rash onset and at >20 weeks gestation. Counsel about symptoms of pneumonia and neurological signs. Referral to foetal medicine specialist with serial US examination 5 weeks post infection

Question 12

Describe varicella vaccination

Answer 12

If a woman is found to be seronegative for varicella zoster IgG pre pregnancy or post partum vaccination should be considered. Do not give during pregnancy

Question 13

What is the percentage risk of varicella infection of the newborn?

Answer 13

50%

Question 14

Describe the route of infection causing varicella of the newborn

Answer 14

Transplacental
Vaginal
Direct contact after birth

Question 15

How is varicella of the newborn treated?

Answer 15

Varicella zoster immunoglobulin and Aciclovir

Question 16

What is foetal varicella syndrome caused by?

Answer 16

Subsequent reactivation of the virus in utero as herpes zoster

Question 17

When does reactivation of herpes zoster occur?

Answer 17

Before 20 weeks gestation if foetal infected with maternal varicella

Question 18

What are the features of foetal varicella syndrome?

Answer 18

Skin scarring in a dermatomal distribution
Eye defects - microphthalmia, choriorenitis, cataracts, optic atrophy
Hypoplasia of limbs
Neurological abnormalities
Neurological abnormalities - microcephaly, cortical and spinal cord atrophy, seizures, horners syndrome